Little is known about the mechanisms of transport of neurotropic viruses, such as Herpes simplex virus (HSV), varicella-zoster virus and rabies, within neuroses. For these viruses, which replicate in the nucleus, anterograde transport from the cell body of dorsal root human ganglionic (DRG) neurons to the axon terminus occurs over long distances. In the case of HSV, there is increasing evidence for separate, fast anterograde axonal transport of viral nucleocapsids coated with tegument along microtubules (MTs) and of glycoproteins in axonal transport vesicles. An understanding of the mechanisms of transport of these viruses would be of benefit. Once this information is obtained, means to interrupt or prevent this transport would be a good candidate for antiviral therapy.
HSV consists of an outer lipid envelope containing glycoproteins which surrounds the tegument. The inner capsid encloses the viral DNA to form the nucleocapsid. Early work has shown that HSV retrograde axonal transport in rat neurons utilizes microtubules (K. Kristensson, E. Lycke, J. Sjostranid, Acta Neuropathol, 17, 44, 1971). Previously, the present inventors have used a two chamber system to examine the mechanism of anterograde transport of HSV from infected dorsal root ganglionic (DRG) neurones in the central chamber along axonal fascicles to epidermal explants in the outer chamber. The velocity of viral transport (0.6 μm/s) indicated a mechanism based on fast anterograde transport (M. E. Penfold. P. Armati. A. L. Cunningham, Proc. Natl. Acad. Sci. USA 91, 6529, 1994). Using freeze-substitution transmission immuno-electron microscopy (TIEM) the virus was shown to be transported as unenveloped nucleocapsids, coated with tegument, separately from glycoproteins which are transported in vesicles (D. J. Holland, M. Miranda-Saksena, R. A. Boadle, P. J. Armati, A. L. Cunningham, J. Virol. 73, 8476, 1999). These findings were supported by experiments with nocodazole, an inhibitor of microtubule polymerization, and brefeldin A which inhibits transport through the Golgi. The transport of all three viral components, nucleocapsid, tegument and glycoproteins was inhibited by nocodazole, indicated their dependence on microtubule-associated transport. Brefeldin A, however, inhibited glycoprotein transport but not nucleocapsids confirming that the two are transported along separate pathways and indicating the close association of HSV glycoproteins with Golgi/intermediate compartment membranes.
The present inventors have now obtained useful evidence for the direct interaction between a viral structural tegument protein and an ubiquitous cellular protein. This new information has been used to develop methods and compositions to alter viral transport and movement in cells.